GCD The Largest

DESCRIPTION
Given N, print the largest number that can be achieved by taking gcd (greatest common divisor) of any two i and j where i != j ,and 1<=i; j<=N.

Input
First line of input will contain the number of test cases,T<=2000. Then T
cases follow. For each case,there is a line containing one integer N where 2<= N<=10^18.

Output
For each case, print one line containing a single integer which is the largest gcd of all pairs of numbers between 1 to N.

Sample input
2
2
5

Sample output
1
2

解题：直接用gcd会超时

#include <cstdio>#include <iostream>#include <cstring>#include <algorithm>using namespace std;int main(){    long long n,t,ans;    while(~scanf("%lld",&n))    {        while(n--)        {            scanf("%lld",&t);            if(t%2)                ans = (t - 1)/2;            else ans = t/2;            cout<< ans <<endl;        }    }    return 0;}